The Cracks That Matter and the Ones That Do Not

Every house in Oklahoma has cracks. Almost all of them mean nothing. A small number mean something significant, and the difference is not the size, it is the direction, the location, the material and whether the crack is doing anything over time.

This article gives you a way to read the cracks in your own house so that you know whether to monitor, to call somebody, or to stop worrying about it.

Why cracks happen at all

Three unrelated causes, and telling them apart is most of the work.

Curing and drying. New concrete shrinks as it cures. New plaster and drywall dry out. A house in its first two years produces cracks that mean nothing at all.

Normal seasonal movement. Materials expand and contract with temperature and humidity. Timber framing moves more than masonry. A crack that opens in August and closes in February is doing exactly what it should.

Foundation movement. Expansive clay soils across northeast Oklahoma swell when wet and shrink when dry, and the shrinking lets parts of a foundation drop, covered in our article on why Tulsa houses move.

The question is never whether your house has cracks. It is whether the crack is telling you something is still moving.

How to read a crack

Direction

• Vertical, thin, in drywall. Usually the least concerning. Common at joints and above openings
• Diagonal, running from the corner of a door or window, wider at one end. More indicative. A diagonal crack that tapers suggests one part of the structure has moved relative to another, and the wide end points toward the movement
• Horizontal in a foundation or basement wall. A different mechanism entirely, usually lateral pressure from soil pushing inward rather than settlement. Generally treated as more serious
• Stair-step in brick or block, following the mortar joints in a staircase pattern. A classic differential movement indicator

Width

Hairline cracks you can barely feel are usually cosmetic. Cracks you can fit a coin edge into are worth documenting. Cracks wide enough to see daylight or admit moisture are worth acting on.

What matters more than the current width is whether it is changing, which is the next section.

Displacement

Run your finger across the crack. If the two sides are flush, it has opened. If one side sits proud of the other, the two parts have moved relative to each other in a second direction as well, which is more significant.

Location and material

The same crack means different things in different materials. Drywall is the most forgiving and cracks first. Plaster on lath in older Midtown Tulsa houses cracks readily and much of it is historic. Brick and block are stiffer, so a crack there indicates more movement than an equivalent crack in drywall. Concrete slabs crack as they cure and a hairline slab crack is normal.

The cracks that are almost always fine

• Hairline vertical cracks at drywall joints, particularly on ceilings
• Fine cracks radiating from the corners of doors and windows, where stress naturally concentrates
• Cracks along the line where a ceiling meets a wall, frequently seasonal
• Hairline shrinkage cracking in a concrete slab, driveway or path
• Cracks in older plaster that have been painted over repeatedly and have not moved in decades
• Small cracks in a house under two years old, which are usually curing and drying
• Cracks that visibly open and close with the seasons but do not progressively widen

The cracks that deserve attention

How to monitor properly, for free

This is the single most useful thing on this page, because a crack that has not moved in a year is a completely different fact to one that has.

1. Photograph each crack with something for scale beside it. A coin or a ruler. Include enough of the surrounding wall to identify the location later
2. Mark the ends. A light pencil mark at each end with the date. If the crack extends past your mark, it is growing
3. Measure the width at a marked point and write it down. A crack gauge costs very little
4. Repeat every three months for a year, so you capture a full seasonal cycle
5. Keep it all in one place with dates

After a year you know whether the movement is active or historic, and that single fact changes what any engineer recommends and what any buyer thinks. It also costs nothing but attention.

Who to call, and in what order

A licensed structural engineer if any of the attention-worthy signs are present. They charge a few hundred dollars for a residential inspection and report, have no financial interest in the outcome, and their report carries weight with lenders, buyers and insurers.

A foundation contractor after that, quoting against the engineer's scope rather than producing their own assessment. Comparing three quotes against one engineered scope is a different exercise to comparing them against each other, covered in our article on foundation repair methods compared.

A plumber with a camera if cracks are accompanied by damp patches on a slab floor, unexplained water use or drainage problems. A slab leak saturating soil under one part of the house is a cause of movement, and it is covered in our article on cast iron drain lines.

Fixing the cause before the crack

Filling a crack does nothing about why it is there, and a filled crack that reopens looks worse than one that was left alone, because now it looks like something was hidden.

If movement is active, deal with moisture first, because uneven moisture is what causes differential movement:

• Guttering that works, with downpipes discharging several feet from the foundation
• Grading that falls away from the house. Check after any landscaping, which frequently reverses it
• Fix any plumbing leak immediately
• Manage large water-seeking trees close to the foundation
• Keep moisture consistent during extended drought rather than letting one side dry out

Cosmetic repair comes after the cause is addressed and after monitoring shows the movement has stopped.

What cracks do to a sale

Our interest, stated plainly, and the honest version includes a part against us.

A buyer's inspector who sees stair-step cracking or significant diagonal cracking will recommend evaluation by a structural engineer. That recommendation frequently ends a financed sale on its own, because the buyer will not proceed without the evaluation and the lender will not fund with the question open.

Once an engineer's report exists it becomes a material fact that follows the property, covered on our page about selling a house with foundation problems. That is why a seller who has been through two failed sales finds the third no easier.

The part against us: if your cracks fall in the "almost always fine" list, do not let anybody, including us, price them as though they were structural. Get an engineer's letter saying the movement is within a tolerable range. A few hundred dollars spent there can be worth many times that at sale, and it may keep you in the financed market entirely, where you will usually net more than we can offer.

Where the movement is real and active and the remediation is comprehensive, that is when we are worth a conversation, and send us the engineer's report because it is more accurate than our own estimate.

The short version